An excellent method of finishing square threads after having cut them in the lathe to very nearly the finished dimensions is with an adjustable die in a suitable stock, such as in [Figs. 1017] and [1018], in which s is a stock having handle h, and containing a die d, secured by a cap c, pivoted at p. To adjust the size of the die, two screws, a and b, are used, a passing through the top half of the die and threading into the half below the split, while b threads into the lower half and abuts against the face of the split in the die, so that, by adjusting these two screws, the wear may be taken up and the size maintained standard. This device is used to take a very light finishing cut only, and is found to answer very well, because it obviates the necessity of fine measurement in finishing the thread. The die d is seated in a recess at the top and at the bottom so as to prevent it moving sideways and coming out.
Lathe Tool Holders for Outside Tools.—When a lathe cutting tool is made from a rectangular bar of steel it requires to be forged to bring it to the required shape at the cutting end, and to avoid this labor, and at the same time attain some other advantages which will be referred to presently, various forms of tool holders are employed.
These holders fasten in the tool post, or tool clamp, and carry short tools, which, from their shapes and the manner in which they are presented to the work, require no forging, and maintain their shapes while requiring a minimum of grinding.
Fig. 1019.
Fig. 1020.